Quantum well intermixing using dielectric caps has been studied using photoluminescence at 77 K. The structures which have been investigated, including shallow depth single quantum wells and multiquantum well waveguiding material, are highly sensitive to the presence of surface defects during annealing. Samples capped with either silicon nitride or silica have shown considerable energy shifts afte...
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The Rayleigh scattering coefficients of fluorine (F) doped silica glasses are investigated experimentally and theoretically. They are measured for F-doped silica glass preforms fabricated by the VAD method. It is clarified that the Rayleigh scattering coefficients of F-doped silica glasses increase with increasing F concentration because the concentration fluctuation increases.
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A new scheme for image sequence coding using the wavelet transform and adaptive vector quantisation is proposed. The transform is used to decompose an image into multiresolution and multiband sub-images. Adaptive vector quantisation is then applied to achieve image data compression with good quality and low bit rate. Experimental results are presented.
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The specific contact resistivity of lattice matched InGaAs/InP p-isotype heterojunction has been measured through the use of an interface transmission line model structure. The measured resistance values are comparable to or greater than those of the metal/semiconductor interface and depend heavily on the doping and the abrupt or graded nature of the interface.
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A shuffle multihop network is presented with routing and processing obtained entirely optically using all-optical AND and XOR gates. Soliton pulses are used to avoid the distortion caused by chromatic dispersion. This network can support a traffic relative to 64 users communicating at 48 Gbit/s achieving a total throughput of approximately 1 Tbit/s.
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An optical FM receiver based on a monoelectrode Fabry-Perot laser, with one antireflection coated facet is reported. The device, biased far above threshold, acts as an FSK discriminator/photodetector. An FSK transmission system, up to 1.5 Gbit/s with -30 dBm sensitivities for 10-9 BER, has been demonstrated using this laser. The speed is limited by the transmitter FM response and not by...
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Preliminary results indicate that a resonant tunnel diode (RTD) oscillator can be optically tuned, frequency modulated, and injection locked. Experiments were performed in which a 2.8 GHz RTD oscillator was frequency modulated from DC to 100 MHz and injection locked over a 150 kHz bandwidth with a laser diode via fibre optics.
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An 'almost-all' optical packet switch architecture is presented, based on two rearrangeably nonblocking stages interconnected by optical delay lines with different amounts of delay. Probability of loss as a function of link use and the size of the switch is investigated. In general, with proper setting of the number of delay lines, the switch can achieve arbitrarily low probability of loss.
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Topological loop (B) and cutset (D) matrices are used to formulate systems of equations in many applications in symbolic network analysis and fault diagnosis of electronic circuits. The minimisation of the number of their nonzero elements leads to more effective manipulation of the resulting equations. A simple and efficient algorithm for the reduction of the number of these nonzero elements is in...
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The average bit error rate (BER) performances of 16 square/star QAM and 16 CPSK/DPSK under Rayleigh fading are theoretically analysed and compared. 16 star QAM is inferior to 16 square QAM, which achieves the best performance, by approximately 4 dB in the required average Eb/N0; however, when compared with differentially encoded square QAM, the performance inferiority is less...
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A simple technique for confining circular-array phase modes to angular sectors is introduced. Each sectoral phase mode (SPM) is a broadband directional beam characterised by an approximately linear phase slope. It is shown that the performance of a multimodal phase-comparison direction-finder in a multiple signal environment and the null steering agility of a multibeam null-steering system may be ...
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A low-frequency oscillator for floating-point DSP chips is reported. The disturbances associated with quantisation errors are strongly reduced when compared with conventional structures, making the proposed oscillator suitable for high performance signal processing in the low-frequency range.
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A one-layer feedforward neural network for fast determination of the maximum or minimum of a set of real values is proposed. The convergence speed of the proposed network is faster than that of the MAXNET of the Hamming network and its modified forms, and the multilayer feedforward MAXNET.
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Tensile-strained single quantum well 20-wavelength distributed feedback laser arrays have been fabricated with a wide wavelength span of 56 nm in the 1.5 mu m wavelength region. The light output is TM-polarised and the average threshold current is 22.8 mA for an 875 mu m long array. A minimum laser linewidth of 180 kHz is measured by a delay self-heterodyne method.
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The first realisation and operation of a representative part of a 72 subscriber star coupler designed for full duplex communications with doubled channel count is reported. Error free operation with coherent multichannel communications has been proved.
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In microwave measurement techniques a separation of the incident wave and the reflected wave of a measurement signal is often required, especially for the determination of the scattering parameters with a network analyser. A more general network than the well known signal divider is proposed.
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A series of irradiation tests on erbium fibre amplifiers using fibres with different erbium and codopant levels show the range of gain losses induced and permit some conclusions about the relative roles of the fibre constituents.
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A novel high frequency switching rectifier, termed the quantum boost series resonant rectifier (QBSRR), is proposed. This rectifier provides the input line AC with a unity power factor. With this proposed scheme, several advantages such as low switching loss and wide output voltage range can be obtained.
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A new technique for fabricating domain inversion regions in -c face LiNbO3 by thermal oxidation of Ti is reported. This technique can minimise refractive index changes in such regions, thus it is suitable for quasiphase-matching (QPM) second harmonic generation (SHG). A prototype QPM waveguide SHG device is also demonstrated.
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A sliding window decorrelating algorithm is developed. It is shown to be near-far resistant both in AWGN and fast fading environments. The algorithm is of particular relevance to base stations in multiuser DS-CDMA mobile radio networks and is shown to alleviate the requirement for a complex power control algorithm to compensate for rapidly varying relative user energies.
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Heating standard telecommunication Ge-doped silica fibres to 1200 degrees C removes the ultraviolet absorption bands believed to be responsible for photosensitivity. Losses at 480 nm induced by exposure to 249 nm laser light are reduced from 30 dB/m to less than 0.8 dB/m in the annealed fibre.
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An all-epitaxial GaAs/GaAlAs optically bistable Fabry-Perot etalon, designed to maximise the band-edge resonant electronic nonlinearity relative to unwanted thermal effects, has been demonstrated to be capable of being held CW in either of the bistable states. Switch times of <40 ns were recorded together with a critical switch power of <700 mu W.
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A statistical approach to the evaluation of the performance of amorphous silicon photoconductive arrays for artificial neural networks is presented. By characterising the nonuniformity of the devices, its effect on a typical two-layer perceptron is investigated. Circuit simulation is employed to prove the theoretical prediction.
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Aims & Scope

Electronics Letters is internationally renowned for its rapid communication of new developments and emerging topics across the broad and interdisciplinary field of modern electronics and electrical engineering.